Band pass filter

ABSTRACT

Aspects of this disclosure relate to a band pass filter that includes LC resonant circuits coupled to each other by a capacitor. A bridge capacitor can be in parallel with series capacitors, in which the series capacitors include the capacitor coupled between the LC resonant circuits. The bridge capacitor can create a transmission zero at a frequency below the passband of the band pass filter. The LC resonant circuits can each include a surface mount capacitor and a conductive trace of the substrate, and an integrated passive device die can include the capacitor. Band pass filters disclosed herein can be relatively compact, provide relatively good out-of-band rejection, and relatively low loss.

CROSS REFERENCE TO PRIORITY APPLICATION

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR § 1.57.This application claims the benefit of priority under 35 U.S.C. § 119(e)of U.S. Provisional Patent Application No. 62/592,943, filed Nov. 30,2017 and titled “FILTER FOR WIRELESS COMMUNICATION SYSTEM,” thedisclosure of which is hereby incorporated by reference in its entiretyherein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to filters, such as band passfilters for wireless communication systems.

Description of Related Technology

A band pass filter passes frequencies within a passband and attenuatesfrequencies above and below the passband. A variety of circuittopologies can implement a band pass filter. Band pass filters have beenimplemented by acoustic wave devices, low temperature co-fired ceramics,or integrated passive devices. A band pass filter with good attenuationoutside of the passband and relatively low insertion loss in thepassband is generally desirable.

Band pass filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include band pass filters. Meeting performancespecifications for certain band pass filters in radio frequencyelectronic systems can be challenging.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

One aspect of this disclosure is a band pass filter that includes afirst LC resonant circuit, a second LC resonant circuit, capacitorsarranged in series with each other, and a bridge capacitor. A capacitorof the capacitors is coupled between the first LC resonant circuit andthe second LC resonant circuit. The band pass filter has a pass band.The bridge capacitor is arranged to create a transmission zero at afrequency below the passband of the band pass filter.

The capacitors and the bridge capacitor can be implemented on anintegrated passive device die. The first LC resonant circuit can includea surface mount capacitor and a conductive trace of a substrate.

The band pass filter can include a second bridge capacitor in parallelwith a subset of the capacitors, in which the capacitors include atleast three capacitors in series with each other. The second bridgecapacitor can be arranged to create a second transmission zero at asecond frequency below the passband of the band pass filter.

The band pass filter can include an LC tank in series between thecapacitors and an output of the band pass filter. The LC tank can bearranged to create an upper transmission zero above the passband.

The first LC resonant circuit can include a shunt inductor in parallelwith a series LC shunt circuit. The series LC shunt circuit can bearranged to create an upper transmission zero at a frequency above thepassband of the band pass filter.

The first LC resonant circuit can include a first series LC shuntcircuit arranged to create a first upper transmission zero at afrequency above the passband, and the second LC resonant circuit caninclude a second series LC shunt circuit arranged to create a secondupper transmission zero at a second frequency above the passband.

A lower bound of the passband can be above 3 gigahertz. The passband canbe from 3.4 gigahertz to 3.8 gigahertz. The passband can be from 3.4gigahertz to 3.6 gigahertz.

Another aspect of this disclosure is a filter assembly that includes afirst LC resonant circuit, a second LC resonant circuit, and anintegrated passive device die on a substrate. The first LC resonantcircuit includes a first conductive trace of the substrate and a firstsurface mount capacitor on the substrate. The second LC resonant circuitincludes a second conductive trace of the substrate and a second surfacemount capacitor on the substrate. The integrated passive device dieincludes a capacitor coupled between the first LC resonant circuit andthe second LC resonant circuit. The capacitor, the first LC resonantcircuit, and the second LC resonant circuit are included in a band passfilter.

The integrated passive device die can include a second capacitor inseries with the capacitor, and a bridge capacitor in parallel with theseries combination of the capacitor and the second capacitor. Theintegrated passive device die can include a third capacitor in serieswith the capacitor and the second capacitor, and a second bridgecapacitor in parallel with the series combination of the capacitor, thesecond capacitor, and the third capacitor.

The first surface mount capacitor can be coupled between the firstconductive trace and ground. The first LC resonant circuit can include aseries LC shunt circuit in parallel with the first conductive trace, inwhich the series LC shunt circuit includes the first surface mountcapacitor. The first surface amount capacitor can be a shunt capacitor,and the first conductive trace can be in parallel with the first surfacemount capacitor. The second surface mount capacitor and the secondconductive trace can be arranged as a parallel LC shunt circuit. Thefilter assembly can include an LC tank circuit coupled between thecapacitor and an output of the band pass filter.

A passband of the band pass filter can have a lower bound above 3gigahertz. A passband of the band pass filter can be from 3.4 gigahertzto 3.8 gigahertz. A passband of the band pass filter can be from 3.4gigahertz to 3.6 gigahertz.

Another aspect of this disclosure is front end module that includes aband pass filter, a power amplifier, a low noise amplifier, and atransmit/receive switch. The band pass filter includes a first LCresonant circuit, a second LC resonant circuit, capacitors arranged inseries with each other and including a capacitor coupled between thefirst LC resonant circuit and the second LC resonant circuit, and abridge capacitor coupled in parallel with the capacitors. The bridgecapacitor arranged to create a transmission zero at a frequency below apassband of the band pass filter. The transmit/receive switch isconfigured to selectively couple the band pass filter to the poweramplifier or the low noise amplifier.

The band pass filter of the front end module can include any suitablefeatures of the band pass filters disclosed herein. The band pass filterof the front end module can include any suitable features of the filterassemblies disclosed herein.

Another aspect of this disclosure is a diversity receive module thatincludes a diversity receive port and a band pass filter. The diversityreceive port is arranged to receive a signal from a diversity antenna.The band pass filter has an input coupled to the diversity receive port.The band pass filter includes a first LC resonant circuit, a second LCresonant circuit, capacitors arranged in series with each other andincluding a capacitor coupled between the first LC resonant circuit andthe second LC resonant circuit, and a bridge capacitor coupled inparallel with the capacitors. The bridge capacitor is arranged to createa transmission zero at a frequency below a passband of the band passfilter.

The band pass filter of the diversity receive module can include anysuitable features of the band pass filters disclosed herein. The bandpass filter of the diversity receive module can include any suitablefeatures of the filter assemblies disclosed herein.

A wireless communication device can include one or more suitablefeatures of any of the band pass filters, filter assemblies, front endmodules, or diversity receive modules disclosed herein.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a filter topology according to anembodiment.

FIG. 2 includes the schematic diagram of FIG. 1 with a graph of afrequency response corresponding to the filter of FIG. 1 according to anembodiment.

FIG. 3 is a schematic diagram of a band pass filter according to anembodiment.

FIG. 4 is a graph of a frequency response corresponding to the band passfilter of FIG. 3 according to an embodiment.

FIG. 5 is a diagram of a layout of a band pass filter of FIG. 3according to an embodiment.

FIG. 6A a schematic diagram of a filter topology according to anembodiment.

FIG. 6B a schematic diagram of a filter topology according to anembodiment.

FIG. 7 is a schematic diagram of a filter topology according to anembodiment.

FIG. 8 is a schematic diagram of a band pass filter according to anembodiment.

FIG. 9 is a graph of a frequency response corresponding to the band passfilter of FIG. 8 according to an embodiment.

FIG. 10 is a schematic diagram of a radio frequency system that includesa band pass filter according to an embodiment.

FIG. 11 is a schematic diagram of another radio frequency system thatincludes a band pass filter according to an embodiment.

FIG. 12 is a schematic diagram of a radio frequency module that includesa band pass filter according to an embodiment.

FIG. 13 is a schematic diagram of another radio frequency module thatincludes a band pass filter according to an embodiment.

FIG. 14 is a schematic diagram of a wireless communication device thatincludes a band pass filter in a radio frequency front end according toan embodiment.

FIG. 15 is a schematic diagram of a wireless communication device thatincludes a first band pass filter in a radio frequency front end and asecond band pass filter in a diversity receive module according to anembodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

A band pass filter (BPF) is a significant component in communicationsystems. There is a need to design BPFs that have a relatively low loss,good out-of-band rejection, compact size, and relatively low cost. SuchBPFs can be integrated in a radio frequency (RF) front end module for amobile device.

Current band pass filters for filtering Ultra High Band (UHB)frequencies integrated in RF front end modules can include acoustic wavefilters such as surface acoustic wave (SAW) filters and/or bulk acousticwave (BAW) filters, Low Temperature Co-Fired Ceramic (LTCC) filters, orintegrated passive device (IPD) filters.

This disclosure provides BPFs with relatively low loss, good out-of-bandrejection, compact size, and relatively low cost. Such BPFs can includefrequency traps into coupled resonators to create transmission zeros atupper frequency bands. Feedback networks of the BPFs can providetransmission zeros at lower frequency bands. Relatively high qualityfactor (Q) surface mount technology (SMT) capacitors can be used forcertain capacitors of the BPFs to provide desirable in-band insertionloss. Relatively small shunt inductors can be implemented on a laminateto provide a desirable Q, which can help reduce loss of the BPF.Relatively less loss sensitive capacitors and high frequency traps canbe implemented on an IPD die for a compact size.

The BPFs discussed herein can realize one or more of the followingadvantages, among others, over state of the art BPFs. BPFs discussedherein can be relatively inexpensive to implement. For example, BPFsdiscussed herein are more cost effective than corresponding acousticwave filters or LTCC filters. This can be due to the BPFs beingimplemented partly on laminate and a compact IPD die. Both laminate andan IPD die are less expensive to fabricate than acoustic wave filtersand LTCC filters. BPFs discussed herein can be compact. For instance,BPFs discussed herein can be significantly smaller than LTCC filters andcomparable in size to acoustic wave filters. BPFs discussed herein canbe relatively low loss. For example, BPFs discussed herein can havelower in-band insertion loss compared to acoustic wave filters andcomparable in-band insertion loss compared to LTCC filters.

FIG. 1 is a schematic diagram of a filter topology according to anembodiment. As illustrated in FIG. 1, a filter 10 includes adirect-coupled resonator filter with feedback 12 and a series LC tank14. The filter 10 can be a band pass filter arranged to pass radiofrequency signals having a frequency above 3 GHz, such as Band 42signals and/or Band 43 signals. The filter 10 can be used in 5thgeneration wireless systems (5G) applications.

The direct-coupled resonator filter with feedback 12 includes a firstbridge capacitor 21, a second bridge capacitor 22, a first LC resonantcircuit 23, a second LC resonant circuit 24, and coupling capacitors 25,26, and 27. The first bridge capacitor 21 has a first end coupled to theseries LC tank 14 and a second end coupled to an input node of thefilter 10. The first bridge capacitor 21 is in parallel with thecoupling capacitors 25, 26, and 27.

The first LC resonant circuit 23 is an LC shunt resonant circuit. Asillustrated, the first LC resonant circuit 23 includes a shunt inductorin parallel with a series LC circuit. The second bridge capacitor 22 hasa first end coupled to the series LC tank 14 and a second end coupledthe first LC resonant circuit 23. The second bridge capacitor 22 is inparallel with the coupling capacitors 26 and 27. The second LC resonantcircuit 24 is an LC shunt resonant circuit. As illustrated, the secondLC resonant circuit 24 includes a shunt inductor in parallel with aseries LC circuit.

A first coupling capacitor 25 is coupled between an input of the filter10 and a node at which the first coupling capacitor 25 is coupled to thefirst LC resonant circuit 23 and the second coupling capacitor 26. Asecond coupling capacitor 26 is coupled in series between the firstcoupling capacitor 25 and the second coupling capacitor 27. The secondcoupling capacitor 26 is also coupled between the first LC resonantcircuit 23 and the second LC resonant circuit 24. A third couplingcapacitor 27 is coupled between series LC tank 14 and a node at whichthe third coupling capacitor 27 is coupled to the second LC resonantcircuit 24 and the second coupling capacitor 26.

The series LC tank 14 is an LC tank arranged in series between thedirect-coupled resonator filter with feedback 12 and an output of thefilter 10. The illustrated series LC tank 14 is a parallel LC circuit.

FIG. 2 includes the schematic diagram of FIG. 1 with a graph of afrequency response corresponding to the filter 10 of FIG. 1 according toan embodiment. The frequency response of FIG. 2 corresponds to a bandpass filter with passband from 3.4 GHz to 3.8 GHz. A filter with such afrequency response can filter Band 42 and Band 43 signals.

FIG. 2 also indicates how circuit elements of the filter 10 cancontribute to the frequency response of the filter 10. As shown in FIG.2, lower-band transmission zeros can be controlled by feedback networkscreated by the bridge capacitors 21 and 22. Each of the bridgecapacitors 21 and 22 can create a separate transmission zero at arespective frequency below the passband of the filter 10. In thefrequency response shown in FIG. 2, these transmission zeros are ataround 1.8 GHz and 2.4 GHz. The bridge capacitors can have respectivecapacitances so as to create transmission zeros at particularfrequencies. These transmission zeros can correspond to frequencieswhere other signals, such as signals associated with different carriersthan the input signal to the filter 10 in a carrier aggregation system,in the system are located. Accordingly, the filter 10 can provide strongrejection to reduce and/or eliminate noise from the other signals. Thebridge capacitors 21 and 22 can have capacitances of a couple ofpicofarads (pF) or less in certain applications.

A method of filtering a radio frequency signal with a band pass filter,such as the filter 10 with the frequency response shown in FIG. 2, isprovided. The method includes receiving the radio frequency signal at aninput port of the band pass filter. The band pass filter has a passband.The band pass filter includes a first LC resonant circuit, a second LCresonant circuit, capacitors arranged in series with each other in whicha capacitor of the capacitors is coupled between the first LC resonantcircuit and the second LC resonant circuit, and a bridge capacitorcoupled in parallel with the capacitors. The method includes filteringthe radio frequency signal with the band pass filter such that atransmission zero is created at a frequency below the passband of theband pass filter.

The filtering can include creating, with a second bridge capacitor inparallel with a subset of the capacitors, a second transmission zero ata second frequency below the passband of the band pass filter.Alternatively or additionally, the filtering can include creating, withan LC tank in series between the capacitors and an output of the bandpass filter, an upper transmission zero at a frequency above thepassband.

In certain instances, the filtering can include creating, with a seriesLC shunt circuit of the first LC resonant circuit, an upper transmissionzero at a frequency above the passband of the band pass filter. In someof such instances, the filtering can include creating, with a secondseries LC shunt circuit of the second LC resonant circuit, a secondupper transmission zero at a second frequency above the passband.

The method can include filtering a radio frequency signal having afrequency of more than 3 gigahertz, such as a signal having a frequencyin a range from 3.4 gigahertz to 3.8 gigahertz.

The method can include using a band pass filter with any suitablecombination of features of the band pass filter 10 of FIG. 1. Thefiltering of the method can involve filtering a radio frequency signalso as to create any suitable features of the frequency response shown inFIG. 2.

FIG. 2 also illustrates that upper-band transmission zeros can becreated by shunt LC circuits of the LC resonant circuits 23 and 24,respectively. The capacitance and inductance of each of the LC shuntcircuits can be arranged to provide a transmission zero at a desiredfrequency. These transmission zeros can be at harmonics of other signalsof the system. An extra upper-band transmission zero can be created bythe series LC tank 14. The inductance and capacitance of the series LCtank 14 can be selected to create this extra upper-band transmissionzero at a desired frequency. For instance, an extra upper transmissionzero can be at a second harmonic of a 5 GHz Wi-Fi signal.

FIG. 3 is a schematic diagram of a band pass filter 30 according to anembodiment. The band pass filter 30 can be a Band 42/Band 43 band passfilter with harmonic rejections for a power amplifier front end module.The band pass filter 30 is a hybrid design that includes circuitelements of different technologies. The band pass filter 30 includesintegrated passive devices (IPDs) on an IPD die, conductive traces of alaminate, and surface mount capacitors. A filter assembly can includethe illustrated circuit elements of the band pass filter 30.

The band pass filter 30 has the same circuit topology as the filter 10of FIG. 1. In the band pass filter 30, certain circuit elements areimplemented by various technologies. As shown in FIG. 3, a first bridgecapacitor 31, a second bridge capacitor 32, coupling capacitors 35, 36,and 37, and a series LC tank 38 are implemented by IPDs. Theseintegrated passive devices can be implemented on a single IPD die.

Inductors 42 of a first LC resonant circuit 33 can be implemented byconductive traces of a laminate substrate (e.g., the conductive tracescan be on and/or in the laminate substrate). Capacitor 41 of the firstLC resonant circuit 33 can be a surface mount capacitor.

Inductors 44 of a second LC resonant circuit 34 can be implemented byconductive traces of the laminate substrate (e.g., the conductive tracescan be on and/or in the laminate substrate). Capacitor 43 of the secondLC resonant circuit 34 can be a surface mount capacitor. The band passfilter 30 can be shared for both transmit and receive paths in a radiofrequency front end. With The band pass filter 30, an external acousticfilter for the receive path can be omitted.

FIG. 4 is a graph of simulation results a frequency responsecorresponding to the band pass filter 30 of FIG. 3 according to anembodiment. This simulation is for a Band 42/Band 43 band pass filterdesign with harmonic rejection. For this simulation, the IPD capacitorshave a Q of 70 at 3.5 GHz, the SMT capacitors have a Q of 120 at 3.5GHz, and the conductive traces have a Q of about 50 at 3.5 GHz. Theseexample Q values are in a typical range of Q values for the varioustechnologies, although other Q values can be implemented. As shown inFIG. 4, the band pass filter 30 can cover both Band 42 and Band 43 within-band insertion loss better than 1.8 dB. As also shown by FIG. 4, theband pass filter can provide good out-of-band rejections for Band 1,Band 3, Band 5, Band 41 and low/high-band Wi-Fi. The band pass filter 30can also provide harmonic rejections, which are typically desired for apower amplifier front end module.

FIG. 5 is a diagram of a filter assembly 50 according to an embodiment.The filter assembly 50 illustrates an example layout for the band passfilter 30 of FIG. 3. The filter assembly 50 can include a band passfilter for Band 42 and/or Band 43. Such a band pass filter can have apassband from 3.4 GHz to 3.8 GHz, for example. The filter assembly 50includes an IPD die 52 and a surface mount device and laminate coilsection 54.

The IPD die 52 can include the IPDs of the band pass filter 30 of FIG.3. For instance, the IPDs can include bridge capacitors 31 and 32,coupling capacitors 35, 36, and 37, and a capacitor and an inductor ofan LC tank 38.

The surface mount device and laminate coil section 54 includes a firstsurface mount capacitor 61 and a second surface mount capacitor 63.These surface mount capacitors are shunt capacitors of LC resonantcircuits as illustrated. The surface mount capacitors 61 and 63correspond to the surface mount capacitors 41 and 42, respectively, ofFIG. 3. The surface mount device and laminate coil section 54 alsoincludes conductive traces 62A, 62B, 64A, and 64B on and/or in alaminate substrate. These conductive traces can be printed coils on alaminate substrate or any other suitable packaging substrate. Theconductive traces 62A and 62B can correspond to the inductors 42 of FIG.3. The conductive traces 64A and 64B can correspond to the inductors 44of FIG. 3.

A method of manufacturing a filter assembly, such as the filter assembly50 of FIG. 5, is provided. The method includes providing a substratewith conductive traces on and/or in a substrate. The method includesmounting surface mount capacitors on the substrate such that theconductive traces and the surface mount capacitors form at least a firstresonant LC circuit and a second resonant LC circuit. The methodincludes attaching an integrated passive device die on a substrate.After the mounting and the attaching, a band pass filter includes thefirst LC resonant circuit, the second LC resonant circuit, and acapacitor of the integrated passive device die. The capacitor is coupledbetween the first LC resonant circuit and the second LC resonantcircuit.

The band pass filter can include additional capacitors of the integratedpassive device die. For instance, the band pass filter can include asecond capacitor of the integrated passive device die in series with thecapacitor, and a bridge capacitor of the integrated passive device diein parallel with the series combination of the capacitor and the secondcapacitor. In some such instances, the band pass filter can include athird capacitor of the integrated passive device die in series with thecapacitor and the second capacitor, and a second bridge capacitor of theintegrated passive device die in parallel with the series combination ofthe capacitor, the second capacitor, and the third capacitor. The bandpass filter can include an LC tank of the integrated passive device diecoupled between the capacitor and an output of the band pass filter.

The attaching the integrated passive devices die can include flip chipmounting the integrated passive devices die on the substrate andconnecting the integrated passive devices die to bump pads on thesubstrate with bumps. Alternatively or additionally, the integratedpassive devices die can be electrically connected to one or more pads ofthe substrate by one or more respective wire bonds.

The mounting the surface mount capacitors can electrically connect afirst end of a first surface mount capacitor to ground and electricallyconnect a second end of the first surface mount capacitor to a firstconductive trace of the conductive traces.

The method can include manufacturing a filter assembly that includes aband pass filter with any suitable combination of features of any of theband pass filters disclosed herein. For example, the band pass filtercan include any suitable combination of features of the band pass filter30 of FIG. 3 and/or the band pass filter 80 of FIG. 8.

The principles and advantages of the filters discussed herein can beimplemented in different filter topologies. For example, a differentnumber of bridge capacitors can be implemented in different filters.FIGS. 6A and 6B illustrate filter topologies that include a singlebridge capacitor. The filter 65 of FIG. 6A is like the filter 10 of FIG.1, except that the filter 65 omits the second bridge capacitor 22 of thefilter 10. The filter 65 includes a direct-coupled resonator filter withfeedback 66 with only one bridge capacitor 21. The filter 67 of FIG. 6Bis like the filter 10 of FIG. 1, except that the filter 67 omits thefirst bridge capacitor 21 of the filter 10. The filter 67 includes adirect-coupled resonator filter with feedback 68 with only one bridgecapacitor 22. In some instances, three or more bridge capacitors can beincluded in filter, such as a filter with more resonator tanks thanshown in FIG. 1, FIG. 6A, or FIG. 6B.

FIG. 7 is a schematic diagram of a filter topology according to anembodiment. As illustrated in FIG. 7, a filter 70 includes adirect-coupled resonator filter with feedback 72 and a series LC tank14. The filter 70 is like the filter 10 of FIG. 1 except that the secondLC resonant circuit 74 of the direct-coupled resonator filter withfeedback 72 is different than the second LC resonant circuit 24 ofFIG. 1. The second LC resonant circuit 74 is a parallel LC shuntcircuit. The filter 70 can be a receive filter. For instance, the filter70 can be in a diversity receiver. The filter 70 can be implementedinstead of the filter 10, for example, in applications where a band passfilter does not have stringent harmonic rejection specifications.

FIG. 8 is a schematic diagram of a band pass filter 80 according to anembodiment. The band pass filter 80 can be implemented in a diversityreceive module. For instance, the band pass filter 80 can be a Band42/Band 43 band pass filter without harmonic rejection for a diversityreceive module. The band pass filter 80 can be arranged to filter lowerpower signals than the band pass filter 30 of FIG. 3.

The topology of the band pass filter 80 is similar to the band passfilter 30 of FIG. 3 except that the band pass filter 80 can be designedto optimize and/or enhance performance for a band pass filter in adiversity receiver. The band pass filter 80 can have more stringentrejections at 2.4 GHz Wi-Fi and 5 GHz Wi-Fi than the band pass filter30. The band pass filter 80 can have little or no harmonic rejection.The first and second LC resonant circuits of the band pass filter 80 aredifferent than the corresponding LC resonant circuits of the band passfilter 30. The first LC resonant circuit of the band pass filter 80includes an inductor 81 implemented by an IPD, while the correspondinginductor of the band pass filter 30 is implemented by conductivetrace(s) of a laminate substrate. The inductor 81 on an IPD die can havea lower Q than an inductor implemented by a conductive trace. The bandpass filter 80 can meet diversity receive specifications and implementthe inductor 81 on the IPD die. The second LC resonant circuit of theband pass filter 80 is a parallel LC shunt circuit, while the second LCresonant circuit of the band pass filter 30 is a series LC shunt circuitin parallel with an inductor.

The band pass filter 80 has the same circuit topology as the filter 70of FIG. 7. In the band pass filter 80, certain circuit elements areimplemented by various technologies. As shown in FIG. 8, a first bridgecapacitor 31, a second bridge capacitor 32, coupling capacitors 35, 36,and 37, a series LC tank 38, and an inductor 81 of a first LC resonantcircuit are implemented by IPDs. These integrated passive devices can beimplemented on a single IPD die. Inductor 82 of the first LC resonantcircuit can be implemented by conductive trace(s) on and/or in alaminate substrate. Capacitor 41 of the first LC resonant circuit can bea surface mount capacitor. Inductor 84 of a second LC resonant circuitcan be implemented by conductive trace(s) on and/or in a laminatesubstrate. Capacitor 43 of the second LC resonant circuit can be asurface mount capacitor.

FIG. 9 is a graph corresponding to a simulation of the band pass filterof FIG. 8 according to an embodiment. For this simulation, the IPDcapacitors have a Q of 70 at 3.5 GHz, IPD inductors have a Q of 35 at3.5 GHz, the SMT capacitors have a Q of 120 at 3.5 GHz, and theconductive traces have a Q of 50 at 3.5 GHz. These example Q values arein typical ranges of Q values for the various technologies, althoughother Q values can be implemented. FIG. 9 indicates that in-bandinsertions loss of better than 1.6 dB across Band 42 and Band 43 can beachieved by the band pass filter 80. In this graph, rejection is betterthan 37 dB at 2.4 GHz Wi-Fi and is better than 40 dB at 5 GHz Wi-Fi. Thegraph indicates that the band pass filter 80 can provides rejection ofbetter than 35 dB for at Band 3.

The hybrid filters discussed herein can achieve desirable insertionloss, size, and cost. Acoustic wave filters, such as surface acousticwave filters or film bulk acoustic wave resonator filters, for Band 42are typically used only for receive paths due to limited power handlingcapability at Band 42 frequencies. Acoustic wave filters are compact butcan have higher in-band insertion loss and be costly. As compared toacoustic wave filters, the hybrid filters discussed herein arecomparable in size while lower loss and significantly cheaper. Comparedto LTCC filters, the hybrid filters discussed herein have comparableloss while being cheaper and significantly smaller. Accordingly, thehybrid filters discussed herein provide a desirable combination ofrelatively low insertion loss, relatively small size, and relatively lowcost compared to acoustic wave or LTCC filters for band pass filters forBand 42 and/or similar frequencies.

FIG. 10 is a schematic diagram of a radio frequency system 100 thatincludes a band pass filter 102 according to an embodiment. Asillustrated, the radio frequency system 100 includes the band passfilter 102, a power amplifier 104, a low noise amplifier 106, and atransmit/receive switch 108. The band pass filter 102 can implement anysuitable principles and advantages of any of the band pass filters ofFIG. 1 and/or FIG. 3 and/or FIG. 5. The power amplifier 104 can be anenvelope tracking power amplifier and/or operate in an envelope trackingmode. The radio frequency system 100 can implement time divisionduplexing. The transmit/receive switch 108 can selectively couple theband pass filter 102 to the power amplifier 104 or the low noiseamplifier 106. In some instances, the transmit/receive switch 108 andIPDs of the band pass filter 102 can be implemented on the same die. Asshown in FIG. 10, the band pass filter 102 can be used for transmitfiltering and for receive filtering. The band pass filter 102 can beused to pass radio frequency signals at relatively high frequencies,such as ultra high band radio frequency signals and/or frequencies above3 GHz. As one example, the band pass filter 102 can have a passband ofaround 3.4 GHz to 3.6 GHz for Band 42. As another example, the band passfilter 102 can have a passband of around 3.4 GHz to 3.8 GHz for Band 42and Band 43.

FIG. 11 is a schematic diagram of another radio frequency system 110that includes a band pass filter 111 according to an embodiment. Asillustrated, the radio frequency system 110 includes the band passfilter 111, a low noise amplifier 106, and a radio frequency switch 112.The band pass filter 111 can implement any suitable principles andadvantages of any of the band pass filters of FIG. 7 and/or FIG. 8. Theradio frequency system 110 can be included in a diversity receivemodule. The band pass filter 111 can filter a received radio frequencysignal and provide a filtered radio frequency signal to the low noiseamplifier 106. The radio frequency switch 112 can selectively couple anoutput of the low noise amplifier 106 to a selected receive path. Insome instances, the radio frequency switch 112 and IPDs of the band passfilter 111 can be implemented on the same die. The band pass filter 111can be used to pass radio frequency signals at relatively highfrequencies, such as ultra high band radio frequency signals and/orfrequencies above 3 GHz. As one example, the band pass filter 111 canhave a passband of around 3.4 GHz to 3.6 GHz for Band 42. As anotherexample, the band pass filter 111 can have a passband of around 3.4 GHzto 3.8 GHz for Band 42 and Band 43.

FIG. 12 is a schematic diagram of a radio frequency module 120 thatincludes a band pass filter 102 according to an embodiment. The radiofrequency module 120 can include the radio frequency system 100 of FIG.10. As illustrated, the radio frequency module 120 includes a band passfilter 102, a power amplifier die 122 that includes a power amplifier,and a silicon-on-insulator die 124 that includes the low noise amplifier106 and a switch 126. The switch 126 can be a transmit/receive switch,such as the transmit/receive switch 108 of FIG. 10. The radio frequencymodule 120 can be a front end module.

FIG. 13 is a schematic diagram of another radio frequency module 130that includes a band pass filter 111 according to an embodiment. Theradio frequency module 130 can include the radio frequency system 110 ofFIG. 11. As illustrated, the radio frequency module 130 includes a bandpass filter 111, a low noise amplifier 106, and a switch 132. The lownoise amplifier 106 and the switch 132 can be implemented on asilicon-on-insulator die. In certain instances, the switch 132 can be areceive switch. In some instances, the switch 132 can be atransmit/receive switch. The radio frequency module 130 can be adiversity receive module. In such instances, the radio frequency module130 can include a diversity receive port configured to receive a radiosignal from a diversity antenna. The band pass filter 111 can receivethe radio frequency signal from the diversity receive port.

FIG. 14 is a schematic diagram of a wireless communication 140 devicethat includes a band pass filter 143 in a radio frequency front end 142according to an embodiment. The wireless communication device 140 can beany suitable wireless communication device. For instance, a wirelesscommunication device 140 can be a mobile phone, such as a smart phone.As illustrated, the wireless communication device 140 includes anantenna 141, an RF front end 142 that includes a band pass filter 143, atransceiver 144, a processor 145, and a memory 146. The antenna 141 cantransmit RF signals provided by the RF front end 142. Such RF signalscan include carrier aggregation signals. The antenna 141 can providereceived RF signals to the RF front end 142 for processing. Such RFsignals can include carrier aggregation signals.

The RF front end 142 can include one or more power amplifiers, one ormore low noise amplifiers, RF switches, receive filters, transmitfilters, duplex filters, multiplexers, frequency multiplexing circuits,or any combination thereof. The RF front end 142 can transmit andreceive RF signals associated with any suitable communication standards.The filter 143 can be implemented in accordance with any suitableprinciples and advantages of the filters discussed herein. For instance,the filter 143 can implement any suitable combination of featuresdisclosed with reference to any of FIGS. 1 to 6B.

The transceiver 144 can provide RF signals to the RF front end 142 foramplification and/or other processing. The transceiver 144 can alsoprocess an RF signal provided by a low noise amplifier of the RF frontend 142. The transceiver 144 is in communication with the processor 145.The processor 145 can be a baseband processor. The processor 145 canprovide any suitable base band processing functions for the wirelesscommunication device 140. The memory 146 can be accessed by theprocessor 145. The memory 146 can store any suitable data for thewireless communication device 140.

FIG. 15 is a schematic diagram of a wireless communication device 150that includes a first band pass filter 143 in a radio frequency frontend 142 and a second band pass filter 153 in a diversity receive module152 according to an embodiment. The wireless communication device 150 islike the wireless communication device 140 of FIG. 14, except that thewireless communication device 150 also includes diversity receivefeatures. As illustrated in FIG. 15, the wireless communication device150 includes a diversity antenna 151, a diversity module 152 configuredto process signals received by the diversity antenna 151 and including afilter 153, and a transceiver 154 in communication with both the radiofrequency front end 142 and the diversity receive module 152. The filter153 can be implemented in accordance with any suitable principles andadvantages of the filters discussed herein. For instance, the filter 153can implement any suitable combination of features disclosed withreference to any of FIGS. 7 to 9.

Any of the principles and advantages discussed herein can be applied toother suitable systems, modules, chips, filters, wireless communicationdevices, and methods not just to the systems, modules, chips, filters,wireless communication devices, and methods described above. Theelements and operations of the various embodiments described above canbe combined to provide further embodiments. Any of the principles andadvantages discussed herein can be implemented in association with radiofrequency circuits configured to process signals in a range from about30 kHz to 300 GHz, such as in a range from about 450 MHz to 8.5 GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as chips and/or packaged radio frequencymodules, electronic test equipment, uplink wireless communicationdevices, personal area network communication devices, etc. Examples ofthe consumer electronic products can include, but are not limited to, amobile phone such as a smart phone, a wearable computing device such asa smart watch or an ear piece, a telephone, a television, a computermonitor, a computer, a router, a modem, a hand-held computer, a laptopcomputer, a tablet computer, a personal digital assistant (PDA), avehicular electronics system such as an automotive electronics system, amicrowave, a refrigerator, a stereo system, a digital music player, acamera such as a digital camera, a portable memory chip, a householdappliance, etc. Further, the electronic devices can include unfinishedproducts.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” “for example,” “such as” and the like, unlessspecifically stated otherwise or otherwise understood within the contextas used, is generally intended to convey that certain embodimentsinclude, while other embodiments do not include, certain features,elements and/or states. The word “coupled,” as generally used herein,refers to two or more elements that may be either directly coupled toeach other, or coupled by way of one or more intermediate elements.Likewise, the word “connected,” as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel devices, chips, methods,apparatus, and systems described herein may be embodied in a variety ofother forms. Furthermore, various omissions, substitutions and changesin the form of the methods, apparatus, and systems described herein maybe made without departing from the spirit of the disclosure. Forexample, circuit blocks described herein may be deleted, moved, added,subdivided, combined, and/or modified. Each of these circuit blocks maybe implemented in a variety of different ways. The accompanying claimsand their equivalents are intended to cover any such forms ormodifications as would fall within the scope and spirit of thedisclosure.

What is claimed is:
 1. A band pass filter comprising: a first LCresonant circuit; a second LC resonant circuit; capacitors arranged inseries with each other, a capacitor of the capacitors being coupledbetween the first LC resonant circuit and the second LC resonantcircuit; and a bridge capacitor coupled in parallel with the capacitors,the band pass filter having a pass band, and the bridge capacitorarranged to create a transmission zero at a frequency below the passbandof the band pass filter.
 2. The band pass filter of claim 1 wherein thecapacitors and the bridge capacitor are implemented on an integratedpassive device die, and the first LC resonant circuit includes a surfacemount capacitor and a conductive trace of a substrate.
 3. The band passfilter of claim 1 further comprising a second bridge capacitor inparallel with a subset of the capacitors, the capacitors including atleast three capacitors in series with each other, and the second bridgecapacitor arranged to create a second transmission zero at a secondfrequency below the passband of the band pass filter.
 4. The band passfilter of claim 1 further comprising an LC tank in series between thecapacitors and an output of the band pass filter, the LC tank arrangedto create an upper transmission zero at a frequency above the passband.5. The band pass filter of claim 1 wherein the first LC resonant circuitincludes a shunt inductor in parallel with a series LC shunt circuit,the series LC shunt circuit arranged to create an upper transmissionzero at a frequency above the passband of the band pass filter.
 6. Theband pass filter of claim 1 wherein the first LC resonant circuitincludes a first series LC shunt circuit arranged to create a firstupper transmission zero at a first frequency above the passband, and thesecond LC resonant circuit includes a second series LC shunt circuitarranged to create a second upper transmission zero at a secondfrequency above the passband.
 7. The band pass filter of claim 1 whereinthe passband is from 3.4 gigahertz to 3.8 gigahertz.
 8. The band passfilter of claim 1 wherein the passband is from 3.4 gigahertz to 3.6gigahertz.
 9. A filter assembly comprising: a first LC resonant circuitincluding a first conductive trace of a substrate and a first surfacemount capacitor on the substrate; a second LC resonant circuit includinga second conductive trace of the substrate and a second surface mountcapacitor on the substrate; and an integrated passive device die on thesubstrate, the integrated passive device die including a capacitorcoupled between the first LC resonant circuit and the second LC resonantcircuit; the capacitor, the first LC resonant circuit, and the second LCresonant circuit being included in a band pass filter.
 10. The filterassembly of claim 9 wherein the integrated passive device die includes asecond capacitor in series with the capacitor, and a bridge capacitor inparallel with the series combination of the capacitor and the secondcapacitor.
 11. The filter assembly of claim 10 wherein the integratedpassive device die includes a third capacitor in series with thecapacitor and the second capacitor, and a second bridge capacitor inparallel with the series combination of the capacitor, the secondcapacitor, and the third capacitor.
 12. The filter assembly of claim 9wherein the first surface mount capacitor is coupled between the firstconductive trace and ground.
 13. The filter assembly of claim 9 whereinthe first LC resonant circuit includes a series LC shunt circuit inparallel with the first conductive trace, the series LC shunt circuitincluding the first surface mount capacitor.
 14. The filter assembly ofclaim 9 wherein the first surface amount capacitor is a shunt capacitor,and the first conductive trace is in parallel with the first surfacemount capacitor.
 15. The filter assembly of claim 9 further comprisingan LC tank circuit coupled between the capacitor and an output of theband pass filter.
 16. The filter assembly of claim 9 wherein a passbandof the band pass filter has a lower bound above 3 gigahertz.
 17. Thefilter assembly of claim 9 wherein a passband of the band pass filter isfrom 3.4 gigahertz to 3.8 gigahertz.
 18. A front end module comprising:a band pass filter including a first LC resonant circuit, a second LCresonant circuit, capacitors arranged in series with each other andincluding a capacitor coupled between the first LC resonant circuit andthe second LC resonant circuit, and a bridge capacitor coupled inparallel with the capacitors, the bridge capacitor arranged to create atransmission zero below a passband of the band pass filter; a poweramplifier; a low noise amplifier; and a transmit/receive switchconfigured to selectively couple the band pass filter to the poweramplifier or the low noise amplifier.
 19. The front end module of claim18 wherein the capacitors and the bridge capacitor are implemented on anintegrated passive device die, and the first LC resonant circuitincludes a surface mount capacitor and a conductive trace of asubstrate.
 20. The front end module of claim 18 further comprising an LCtank in series between the capacitors and an output of the band passfilter, the LC tank arranged to create an upper transmission zero at afrequency above the passband.